My last time change was for the last leg of an ex-Eur ticket, LGW-KRK, which I was not intending to use anyway. As they moved the flight forward 3 hours, I called and said this was no longer convenient and what were my options. They asked what I wanted to do. "How about change the LGW-KRK for a few weeks later?". No problem, they said, and I now have a separate trip lined up (this was a non-changeable T/Y class upgraded to U class, with no stopovers allowed in the UK).